interesting .. Halachapedia refers to Shulchan Aruch 251:1, Mishna Brurah 251:5, discussing not starting new jobs after mincha.
The wuestion is – are you viewing sharpening pencils as the first task in your yom rishon job, or do you just feel that a good engineer needs to keep his pencil sharpened? If you have an extra hour after you sharpen your pencil, would you be tempted to start the drawing? If yes, then it falls under “new job” category
It is hard for me to relate, as I don’t think I sharpened my pencils this century .. But now am I right, when I train machine learning models, I prepare several versions and have it run over shabbat. Am I right doing thaty before shabbat and also making my computer chum in the corner (or in the cloud)?